已知角α终边上有一点p(4t,-3t)(t≠0),求2sinα+cosα的值
人气:267 ℃ 时间:2020-05-09 04:09:13
解答
用a代替
x=4t
y=-3t
则r=√(x²-y²)=5|t|
sina=y/r=-3t/5|t|
cosa=x/r=4t/5|t|
所以t>0,sina=-3/5,cpsa=4/5
t<0,sina=3/5,cpsa=-4/5
所以
t>0,原式=-2/5
t<0,原式=2/5
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